1. Field of the Invention
The present invention relates to a projection type display apparatus, and more particularly, to a projection type display apparatus capable of changing flow of air generated when a color wheel filtering light projected from a light source rotates, thereby reducing noise.
2. Description of the Prior Art
In general, a projection type display apparatus adopts a principle that an image is projected on a screen by means of a mirror and an optical lens. Such a projection type display apparatus includes a projector or a projection television.
In particular, the projection television is an apparatus which realizes a large scale screen using the above principle, and is classified into a CRT (Cathode Ray Tube) projection television, an LCD (Liquid Crystal Display) projection television, and a DLP (Digital Light Processing) projection television according to a display device thereof that displays signal-processed image information.
The projection television includes a light source emitting white light and a color wheel which is provided adjacent to the light source so as to allow red R, green G and blue B light components of the white light to selectively pass through the color wheel.
Since the color wheel is a rotating member in which a color rotation plate is rotated by means of a driving source at a high speed of 9000 RPM or above, noise occurs due to the rotation of the color wheel.
As shown in FIG. 1, the color wheel 50 is housed in a color wheel housing 70, and an upper portion and one side portion of the color wheel housing 70 are opened. The opened portions of the color wheel housing 70 can be closed by a color wheel holder 80. In addition, a sealing member 90 made from rubber is interposed between the color wheel housing 70 and the color wheel holder 80 so as to prevent noise and vibration caused by an operation of the color wheel 50.
Meanwhile, a light source 40 is provided at one side of the color wheel housing 70 so as to irradiate light and a UV filter 82 filtering UV components of light projected from the light source 40 is installed on the color wheel holder 80.
In addition, the color wheel housing 70 is provided with an optical tunnel 60 through which light filtered by the color wheel 50 passes. In addition, a panel section (not shown) and a projection lens projecting an image generated from the panel section onto a reflective mirror (not shown) are provided while being spaced apart from the optical tunnel 60 by a predetermined distance.
Here, the panel section has a DMD (Digital Micro-mirror Device) and serves to generate the image based on the light of an optical part by controlling a reflective angle of each pixel.
The light is uniformly distributed via the optical tunnel 60, so that the image is created on the panel section (not shown), and the image is displayed on a display unit (not shown) through a projection lens (not shown) and a reflective mirror (not shown).
However, when the color wheel 50 rotates in the conventional color wheel housing 70, noise and vibration are generated due to the rotation of the color wheel 50. Accordingly, as described above, the sealing member 90 is provided between the color wheel housing 70 and the color wheel holder 80 so as to prevent the noise and the vibration from being mechanically applied to the color wheel housing 70 and the color wheel holder 80.
However, when the color wheel 50 rotates at the high speed, a high-speed air flow occurs in an inner space formed between the color wheel housing 70 and the color wheel holder 80. Due to the characteristics of the air flow and a collision between the air flow and an inner wall of the color wheel housing 70 and the color wheel holder 80, noise and vibration are generated. Such noise and vibration cannot be effectively prevented by using the sealing member 90.
In addition, most of the energy of the high-speed air flow is converted into thermal energy, so that the life span of compartments including the color wheel housing 70 is shortened and reliability of the product is degraded.
In particular, when light irradiated from the light source 40 has passed through the color wheel 50, some of light is utilized and the remaining parts of light are wasted, thereby incurring a transmission loss of light. In this case, it is necessary to enlarge a size of the color wheel 50 or to increase the RPM of the color wheel 50 in order to ensure a sufficient amount of light. However, acoustic noise is significantly increased when the size or the RPM of the color wheel 50 is increased.